Hospitals caring for elderly Medicare beneficiaries face unprecedented pressure to reduce unwanted practice variation and costs of hospitalization. To achieve these goals in surgical care, a growing number have introduced Enhanced Recovery After Surgery (ERAS) protocols -- multidisciplinary bundles of surgical, anesthetic, nursing, and medical care intended to reduce the physiologic stress of surgery. In studies from highly specialized centers where they were developed, ERAS protocols have achieved faster recovery and shorter length of stay after major inpatient surgery. Yet it remains unclear whether such protocols improve costs and outcomes of surgical episodes overall, or simply shift them from the hospital to outpatient setting. Further, it is unknown whether ERAS will be effective for the most vulnerable patients, especially older adults with multiple comorbid conditions, who account for an increasing share of major surgery and often require ancillary care services after index hospitalization. Capitalizing on the unique data infrastructure in the state of Michigan, wit rich surgical outcomes, cost and utilization data, this proposal will evaluate ERAS in real-world surgical care, and assess its clinical, economic, and functional outcomes for frail and elderly patients. The specific research aims are to evaluate: (i) clinical outcomes of ERAS in real-world surgical practice; (ii) effects of ERAS on cost and utilization across the entire surgical episode; and (iii) differential effects of ERAS by age and comorbidity. As the first population-based assessment of ERAS protocols for inpatient surgery, this study will have immediate impact on efforts to improve efficiency of inpatient surgical care, and will provide a generalizable assessment of the viability of ERAS for value-based care delivery in US hospitals. Further, the research project, highly experienced multidisciplinary mentorship team, and unparalleled research environment are ideally suited to address the career goals and educational needs of the candidate, Scott Regenbogen, MD, MPH. The proposal includes a detailed educational plan with training that will be essential both for successful completion of this research and toward Dr. Regenbogen's career development in both health services and clinical aging research around geriatric surgery. The training includes graduate level courses in health care delivery systems, causal inference, and gerontology, as well as rotations in clinical geriatrics, with a focus on the acute and transitional care of complex elderly surgical patients. This career development award will lay the groundwork for Dr. Regenbogen to perform ongoing, innovative health services research, and to become an independent investigator and national leader in quality improvement around the unique needs of older adults undergoing major inpatient surgery.